The specific objectives of this study are to delineate behavioral and biological factors that predict treatment outcome in patients with cocaine dependence drug the first year following hospitalization. Both patient characteristics upon entry into treatment and early changes that take place during treatment will be measured. Eight-five patients admitted to the McLean Hospital Alcohol and Drug Abuse Treatment Center for cocaine dependence will be evaluated carefully in the hospital and will be followed monthly thereafter for one year. A central feature of this study will be frequent monitoring of many dimensions of patients' progress, in order to further understand the processes of recovery and relapse. Patients will attend monthly follow-up meetings (with the exception of the first month, during which they will attend two follow- up meetings) and will fill out brief questionnaires weekly for one year following hospitalization to monitor progress. Specific independent variables to be studied will include psychiatric co-morbidity, gender, and substance abuse history, in order to examine the effect of these variables on treatment outcome. Another subject to be studied in this proposal is the cocaine withdrawal syndrome. Patients will be monitored daily in the hospital and weekly thereafter in order to a) more clearly delineate the nature of the cocaine abstinence syndrome; b) investigate whether a protracted withdrawal syndrome exists; and c) develop a rating scale to measure the severity of cocaine withdrawal symptoms. Severity of cocaine craving, cocaine withdrawal symptoms, and plasma prolactin levels will be measured repeatedly over time in an attempt to determine the nature of the relationship between these factors, as well as their relationship to treatment outcome. It is hoped that understanding the impact of patient characteristics on treatment outcome will permit more rational assignment of patients to specific treatment methods.